1. Field of the Invention
The invention concerns a mobile working machine having a chassis supporting the working machine, at least four wheels pair-wise associated with wheel axles and connected to a frame by interposed wheel springs pre-tensionable by the effect of the load exerted on the axle, with two support legs provided laterally one opposite the other on the sides of the frame and associated with one of the wheel axles, preferably the back axle, which have a foot apart which can be extended downwardly and supported on the ground with raising of the chassis off the ground, and at least one blocking mechanism able to selectively release or block the spring path of one of the wheel springs.
2. Description of the Related Art
Mobile working machines, such as cement pump trucks, must be set up stably on the ground at the work site. For this, they are provided with support legs in the area of the front and/or rear axles. Conventionally, prior to the supporting process, the rear axle is so blocked or arrested on the frame of the vehicle chassis, that during the subsequent extension of the foot parts, they do not have any spring action or only slight spring action and the wheels are lifted off of the ground. For this a blocking mechanism is provided, which selectively blocks or releases the spring path of the wheel springs. The arresting of the axle in a case of mobile cement pump trucks is necessary, in order to increase the stability of the vehicle during pivoting out of the distribution mast. The raised rear axle serves at this time as ballast and contributes to the improved stability of the stance. Besides this, in the case of cement pump trucks with rear material receiving containers there is a reduction of the fill height, which is an advantage during filling with cement.
The most commonly employed technique for spring blocking in the case of cement pumpers involves chains, which prior to the bracing are hooked into a hook provided fixed to the frame. It has already been proposed to carry out the bracing process with the aide of a manually operated hydraulic cylinder. For avoiding the danger of an accident and damage, the axle arresting means must again be released after termination of the work process.